浅谈中国街头篮球的发展现状及其对中国职业篮球发展的影响

运用文献资料和逻辑分析法,研究街头篮球起源及发展的文化背景,分析中国街头篮球的发展历程、现状及发展方向,探讨其对中国职业篮球发展的影响。     

矩阵方程组异类约束解的MCG1-3-5算法

借鉴求线性矩阵方程组同类约束解的MCG算法（修正共轭梯度法）,建立了求多个未知矩阵的线性矩阵方程组的一种异类约束解的MCG1-3-5算法,证明了该算法的收敛性。该算法不仅可以判断矩阵方程组的异类约束解是否存在,而且在有异类约束解,且不考虑舍入误差时,可在有限步计算后求得矩阵方程组的一组异类约束解;选取特殊初始矩阵时,求得矩阵方程组的极小范数异类约束解。同时还能求取指定矩阵在该矩阵方程组异类约束解集合中的最佳逼近。算例表明,该算法有效。     

A theory of instruction for introductory programming skills

ABSTRACT

Background and Context: Current introductory instruction fails to identify, structure, and sequence the many skills involved in programming.

Objective: We proposed a theory which identifies four distinct skills that novices learn incrementally. These skills are tracing, writing syntax, comprehending templates (reusable abstractions of programming knowledge), and writing code with templates. We theorized that explicit instruction of these skills decreases cognitive demand.

Method: We conducted an exploratory mixed-methods study and compared students’ exercise completion rates, error rates, ability to explain code, and engagement when learning to program. We compared material that reflects this theory to more traditional material that does not distinguish between skills.

Findings: Teaching skills incrementally resulted in improved completion rate on practice exercises, and decreased error rate and improved understanding of the post-test.

Implications: By structuring programming skills such that they can be taught explicitly and incrementally, we can inform instructional design and improve future research on understanding how novice programmers develop understanding.     

广义(3+1)维KPB方程的对称约化、精确解和守恒律

运用李对称方法得到了(3+1)维Kadomtsev Petviashvili Boussinesq(KPB)方程的对称和约化方程。进而,利用齐次平衡原理和椭圆函数方法得到了方程的精确解。最后,给出了该方程的守恒律。     

《鸿门宴》多媒体辅助教学摭拾

在新兴的电教多媒体教学中,文言文的教学是一个很少涉猎的领域,作者在《鸿门宴》中作了一个尝试,并将电教多媒体渗透到传统启发式教学。文中剖析了利用多媒体辅助手段在文言文教学中激发学生兴趣,酝酿教学情景,感染力强,信息量大等作用,以及使用多媒体教学手段应遵循突破一点,画龙点睛的原则。本文最终得出的结论是：多媒体教学与传统教学不能相互替代,只能取长补短。     

女性胆固醇随年龄变化灰色GM(1,1)预测模型的建立

研究女性胆固醇随年龄变化的趋势.采集大最女性胆固醇数据,以10岁为年龄段,计算每个年龄段健康女性胆固醇平均值,并以女性70岁以下6个年龄段的胆固醇为原始数列,建立了女性胆固醇随年龄变化的灰色系统(GM(1,1))模型预测.后验差检验合格,预测70～79岁、80以上年龄段的女性胆固醇.预测分析结果表明,灰色系统GM(1,...     

Why super sandstorm 2021 in North China?

Severe sandstorms reoccurred in the spring of 2021 after an absence for more than 10 years in North China. The dust source area, located in Mongolia, suffered destructive cooling and warming in early and late winter, which loosened the land. A lack of precipitation, excessive snow melt and strong evaporation resulted in dry soil and exiguous spring vegetation. A super-strong Mongolian cyclone developed on the bare and loose ground, and easily blew and transported large amounts of sand particles into North China. Furthermore, top-ranking anomalies (sea ice shift in the Barents and Kara Sea, and sea surface temperatures in the east Pacific and northwest Atlantic) were found to induce the aforementioned tremendous climate anomalies in the dust source area. Analyses, based on large-ensemble Coupled Model Intercomparison Project Phase 6, yield results identical to the reanalysis data. Thus, the climate variabilities at different latitudes and synoptic disturbances jointly facilitated the strongest spring sandstorm over the last decade.     

Expression of antimicrobial peptide Cecropin P1 in Saccharomyces cerevisiae and its antibacterial and antiviral activity in vitro

BackgroundCecropin P1, acting as an antimicrobial, has a broad-spectrum antibacterial activity with some antiviral and antifungal properties. It is a promising natural alternative to antibiotics which is originally isolated from the pig intestinal parasitic nematode Ascaris suum. Many studies have shown that Cecropin P1 is helpful for the prevention or treatment of clinical diseases. Therefore, it is very necessary to establish a safe, nontoxic, and efficient expression method of Cecropin P1.ResultsThe results indicated that the recombinant protein was about 5.5 kDa showed by Tricine–SDS–PAGE and Western blot. And Cecropin P1 was efficiently secreted and expressed after 12 h of induction, with an increasing yield over the course of the induction. Its maximum concentration was 7.83 mg/L after concentration and purification. In addition, in vitro experiments demonstrated that Cecropin P1 not only exerted a strong inhibitory effect on Escherichia coli, Salmonella sp., Shigella sp., and Pasteurella sp., but also displayed an antiviral activity against PRRSV NADC30-Like strain.ConclusionsCollectively, the strategy of expressing Cecropin P1 in Saccharomyces cerevisiae is harmless, efficient, and safe for cells. In addition, the expressed Cecropin P1 has antiviral and antibacterial properties concurrently.How to cite: Jiang R, Zhang P, Wu X, et al., Expression of antimicrobial peptide Cecropin P1 in Saccharomyces cerevisiae and its antibacterial and antiviral activity in vitro. Electron J Biotechnol 2021;50. https://doi.org/10.1016/j.ejbt.2020.12.006